Cable lug

ABSTRACT

A cable lug for mounting on the end of a cable for making electrical connection between a conductor of the cable and other electrical equipment. The lug includes a palm for connecting the lug to the electrical equipment, a generally elongate cylindrical barrel for receiving therein one end of the cable conductor, and an insert for disposal within the barrel and for extending around and along the inner surface of the barrel to align the lug more concentrically on smaller cables, preferably with the barrel being conveniently made with uniform wall thickness.

RELATED APPLICATIONS

The present application is a National Phase application ofPCT/GB01/02131 filed on May 15, 2001 and published in English, whichclaims priority from application GB 0012804.1 filed on May 25, 2000.

FIELD OF THE INVENTION

This invention relates to a cable lug for mounting on the end of a cablefor making electrical connection between a conductor of the cable andother electrical equipment.

BACKGROUND OF THE INVENTION

Such cable lugs are well known for terminating electrical power cables,and comprise a palm for connecting the lug to the electrical equipment,usually by means of a bolt passing therethrough, and a barrel, integralwith the palm and usually extending therefrom, for receiving the baredend of the conductor therein. The conductor may be retained in the lugbarrel by crimping, or alternatively by means of securing bolts, whichmay be shear head bolts. The conductor may be solid or stranded, andwill usually be of aluminium or copper.

The electrical equipment may be a transformer or switchgear, with thecable lug being connected to a bushing thereof, which may be by means ofa cable adapter (T- or L-shape), such as sold by Tyco ElectronicsRaychem GmbH under the tradename RSTI for example. Insulation of theelectrical connection may alternatively be effected by aheat-recoverable sleeve, also available from Tyco Electronics RaychemGmbH.

Such cable lugs are supplied for use with cables of a defined range ofsizes, effectively diameters, and it is important to select the correctsize lug for the cable. This leads to the need for holding a relativelylarge inventory, and its associated expense. Conventional cable lugsusing bolt securement have an eccentric barrel, with the wall thicknesson one side being greater then on the other side in order to providesufficient length for the threads of the bolts to be gripped therein.This results in the cable being mounted eccentrically with respect tothe lug, which can be disadvantageous when providing electricalinsulation therearound. The thinner wall section, usually diametricallyopposed, allows the weight and cost of the lug to be minimised. It is anobject of the present invention to provide a cable lug that overcomes,or at least alleviates, problems of the known lugs.

SUMMARY OF THE INVENTION

Thus in accordance with one aspect of the present invention, there isprovided a cable lug for mounting on the end of a cable for makingelectrical connection between a conductor of the cable and otherelectrical equipment, wherein the lug comprises a palm for connectingthe lug to the electrical equipment, a generally elongate cylindricalbarrel for receiving therein one end of the cable conductor, an insertfor disposal within the barrel and for extending around and along theinner surface of the barrel, whereby in operation the insert is arrangedto lie between the cable conductor and the inner surface of the lug, andmeans for retaining the insert against movement within the barrel.

The lug of the invention thus has a separate insert, and this allows asingle barrel to be used with a much larger range of cable sizes, theinsert being required and inserted for use with smaller cables. This canenable the barrel to be aligned more nearly concentrically on the cableend over the whole range of sizes, than would be possible withpreviously known lugs. The barrel wall can be, and preferably is, ofsubstantially uniform thickness, which may be more economical tomanufacture than known lugs of varying wall thickness. Further, theretention of the insert ensures good electromechanical securement of thecable conductor in the barrel of the lug. It is envisaged that theinsert will extend only partially around the inner surface of the barrelof the lug, and may extend only partially or substantially the wholelength of the lug barrel.

Advantageously, the insert will be shaped as part of a generallycylindrical surface, for conformity with the inner surface of the barrelof the lug. In this case, the insert will be circumferentially locatedwithin the barrel generally opposite the threaded aperture in the barrelby which the lug is secured to the cable. However, it is also envisagedthat the insert may be of full cylindrical configuration, formed forexample as a single pressing, in which case it is preferably aperturedat diametrically-opposed locations to receive therethrough the means tosecure the insert to the barrel and the means to secure the lug to thecable respectively.

It will be appreciated that retention of the insert is required duringinsertion of the cable conductor into the barrel in order to ensure goodmechanical and electrical connection, and also advantageously prior tosuch insertion. The retaining means may secure the insert againstrotational and/or longitudinal movement in one or both directions. Theretaining means preferably comprises a projection of one of the barreland insert, advantageously, of the insert, and a co-operating apertureof the other. Such interengagement may be provided at any suitablelocation along and around the insert. The aperture may be an indentationor a through-hole. It will be appreciated that two, or more, projectionsand respective apertures may be provided. In a preferred embodiment, theretaining means includes a hole extending completely through the sidewall of the barrel.

Preferably, the cable lug is made of aluminium or copper. Consequently,it is desirable to tin the inner surface of the barrel of the lug, andthe hole therein conveniently allows passivating solution to flow into,through, and out of the barrel. Advantageously, the insert and/or thebarrel is grooved on its inner surface to enhance connection with thecable conductor. Such grooves may extend longitudinally orcircumferentially. Advantageously, the grooves of the barrel are locatedonly over its innermost region, beyond the position at which the lug isfixed to the cable. Preferably, at least one shear head bolt is providedfor securing the lug to the cable. The cable lug of the invention may besized to suit various cable sizes, for example diameters of 95 to 240mm² or 25 to 95 mm².

It is understood that although the cable lug of the present invention isprimarily for use with the termination of a cable, the other electricalequipment may itself comprise another cable. Accordingly, the cable lugmay be employed in a cable joint, formed, for example, by the use of twosuch lugs fitted to respective cables.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of cable lug, each in accordance with the present invention,will now be described, by way of example, with reference to theaccompanying drawings, in which:

FIG. 1 is an isometric view of a first embodiment of lug;

FIG. 2 is a sectional elevation of the lug of FIG. 1;

FIG. 3 is an isometric view of an insert of the lug of FIG. 1;

FIG. 4 is a view of the insert of FIG. 1 having a stud secured therein;

FIG. 5 is a sectional elevation corresponding to FIG. 2 with the insertof FIG. 4 located therein;

FIG. 6 is an isometric view of a second embodiment of lug;

FIG. 7 is a sectional elevation of the lug of FIG. 6;

FIG. 8 is an isometric view of an insert of the lug of FIG. 6;

FIG. 9 is a sectional elevation showing the insert of FIG. 8 located inthe lug of FIG. 7;

FIG. 10 is an isometric view of a third embodiment of lug;

FIG. 11 is an isometric view of an insert of the lug of FIG. 10; and

FIG. 12 is an elevation of a shear head bolt for use in the lug.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring to FIGS. 1 to 5, an aluminium cable lug 2 comprises agenerally rectangular palm 4 having an aperture 6 therethrough, andintegral therewith a generally hollow cylindrical barrel 8, which iselongate and of uniform wall thickness. To one side, the barrel 8 hastwo threaded holes 10 tapped through the side wall thereof, the holes 10being axially and circumferentially offset from one another. A smallerhole 12 extends through the side wall of the cylindrical surface of thebarrel 8 substantially diametrically opposed to the holes 10.

An aluminium insert 14 is shaped so as to have a part-cylindrical form,and is sized so as to fit conformingly within the bore 16 of the lugbarrel 8. As can be seen from FIG. 5, the insert 14 extends somewhatless than half-way around the inner circumference of the lug barrel 8,and substantially three quarters of the length therealong from the openend. The insert 14 has a hole 18 drilled through the curved surfacethereof in such a location that when the insert 14 is disposed withinthe cable lug bore 16, as shown in FIG. 5, the insert hole 18 can bealigned with the barrel hole 12. A stud 20 (FIG. 4) may be inserted intothe hole 18, and arranged to engage the barrel hole 12 (FIG. 5) so assecurely to retain the insert 14 within the barrel 8 of the lug 2against both longitudinal and rotational movement in each direction. Itis preferred that the insert 14 be provided with grooves that extendlongitudinally thereof, and that the inner surface of the barrel 8 beprovided with grooves that extend circumferentially thereof, in eachcase to enhance gripping of the inserted cable conductor.

In operation, an electrical power cable (not shown) has its outer layersstripped so as to expose the conductor at an end thereof, and the baredconductor is inserted into the cable lug bore 16. Two shear head bolts22 (FIG. 12) are screwed into respective of ones of the barrel holes 10and tightened onto the cable conductor so as to urge it tightly againstthe inner surface of the insert 14. Tightening is carried out until thebolt heads 24 shear at a predetermined torque leaving the threaded boltportions 26 enclosed within the wall thickness of the lug barrel 8.

It will appreciated that the positioning of the hole 18 in the insert 14need not be towards one end thereof as shown in FIG. 3, but could beelsewhere in the surface, to align with a correspondingly-located hole12 in the lug barrel 8. The insert stud 20 may either be firmly securedinto the insert 14 and located in the barrel hole 12 as a sliding fit.Alternatively, the insert 14 may be located within the barrel 8 with theholes 18 and 12 in alignment and the stud 20 may subsequently beinserted therethrough from outside the lug so as to secure the insert 14to the barrel 8. It will be appreciated that should the cable that is tobe inserted into the lug 2 be of a larger size, then the insert may bedispensed with.

Referring to the second embodiment of lug 36 shown in FIGS. 6 to 8, acurved part-cylindrical lug insert 30 has a pair of projections 32extending in substantially opposed-radial directions therefrom at oneend. Interengagement of the insert 30 with the barrel 34 of the lug 36is provided by the barrel 34 having a pair of corresponding-positionedslots 38 in the end face 40 thereof, into which the projections 32 are atight sliding fit. The insert 30 is thus retained against rotationalmovement in each direction with respect to the axis of the lug, and alsoagainst being pushed further into the lug barrel when a cable isinserted therein. In a modification of the lug 36, the slots may beL-shaped so that a bayonet connection may be formed by introducing theinsert 30 longitudinally into the barrel 34 and then rotating it tocause the projections 32 to engage the slot extensions.

Referring to the third embodiment shown in FIGS. 10 and 11, a lug 40 hasa substantially cylindrical barrel 42 with a single radial slot 44 inthe end face 46 thereof. A part-cylindrical insert 48 has a longitudinalextension 50 thereof bent through 90 degrees so as to project in aradial direction therefrom. Insertion of the insert 48 into the barrel42 of the lug 40 then results in the projection 50 engaging within theslot 44, thereby to secure the insert 48 against rotational and furtherinward longitudinal movement. FIG. 11 also shows the longitudinalgrooves 52 of the insert 48, as are preferably applied to each of theinserts described herewithin.

It is to be appreciated that various features of the embodimentsdisclosed herein maybe interchanged or combined with each other asappropriate.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few exemplary embodiments ofthis invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe claims. In the claims, means-plus-function clauses are intended tocover the structures described herein as performing the recited functionand not only structural equivalents but also equivalent structures.Therefore, it is to be understood that the foregoing is illustrative ofthe present invention and is not to be construed as limited to thespecific embodiments disclosed, and that modifications to the disclosedembodiments, as well as other embodiments, are intended to be includedwithin the scope of the appended claims. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

What is claimed is:
 1. A cable lug for mounting on the end of a cablefor making electrical connection between a conductor of the cable andother electrical equipment, wherein the lug comprises a palm forconnecting the lug to the electrical equipment, a generally elongatecylindrical barrel for receiving therein one end of the cable conductor,an insert for disposal within the barrel and for extending around andalong an inner surface of the barrel, the insert being arranged to liebetween the cable conductor and the inner surface of the barrel, andmeans for retaining the insert against movement within the barrel, thecable lug further comprising at least one bolt extending through a sidewall of the barrel for securing the cable conductor therein and whereinthe insert is arranged to be retained within the barrel at acircumferential position substantially opposite to the at least onesecuring bolt.
 2. A cable lug according to claim 1, wherein theretaining means is arranged to retain the insert against rotationalmovement, in both rotational directions, with respect to the innersurface of the barrel.
 3. A cable lug according to claim 2, wherein theretaining means is arranged to retain the insert against longitudinalmovement, in both longitudinal directions, with respect to the innersurface of the barrel.
 4. The cable lug of claim 1 wherein the palm ismechanically coupled to the barrel on a first end thereof and the insertis disposed within the barrel through an opening at an opposite end ofthe barrel.
 5. The cable lug of claim 1 wherein the barrel isconductive.
 6. A cable lug according to claim 1, for mounting on the endof a cable for making electrical connection between a conductor of thecable and other electrical equipment, wherein the lug comprises a palmfor connecting the lug to the electrical equipment, a generally elongatecylindrical barrel for receiving therein one end of the cable conductor,an insert for disposal within the barrel and for extending around andalong an inner surface of the barrel, the insert being arranged to liebetween the cable conductor and the inner surface of the barrel, andmeans for retaining the insert against movement within the barrel andwherein the retaining means comprises a projection on one of the barreland the insert and a co-operating aperture in the other of the barreland the insert.
 7. A cable lug according to claim 6, wherein theprojection extends from the insert at one end of the insert and isarranged to engage an aperture in the barrel, which aperture comprises aslot in an end face of the barrel.
 8. A cable lug according to claim 6,wherein the projection comprises a stud extending from an outer surfaceof the insert, and wherein the aperture extends through the innersurface of the barrel.
 9. A cable lug according to claim 6, wherein theinsert has grooves extending longitudinally of an inner surface thereof.10. A cable lug according to claim 6, made substantially of tinnedaluminium.
 11. A cable lug according to claim 6, further comprising atleast one bolt extending through a side wall of the barrel for securingthe cable conductor therein.
 12. A cable lug according to claim 11,wherein the at least one securing bolt comprises a shear head bolt. 13.A cable lug according to claim 11, wherein the insert is arranged to beretained within the barrel at a circumferential position substantiallyopposite to the at least one securing bolt.
 14. The cable lug of claim 6wherein the barrel is conductive.
 15. A cable lug for electricallyconnecting a conductor, the cable lug comprising: an elongate barrelhaving a substantially cylindrical bore extending longitudinally from anend of the barrel, the bore being configured to receive the conductor; acurved insert positioned within the bore and extending longitudinallyalong a first side of the bore and configured to receive the conductorbetween the insert and an opposite side of the bore; and a projection onat least one of the curved insert and the barrel and an aperture in theother of the curved insert and the barrel, the aperture being positionedto receive the projection to limit movement of the insert in the bore.16. The cable lug of claim 15 wherein the insert is curved tosubstantially conform with the first side of the bore at least part wayaround a circumference of the bore.
 17. The cable lug of claim 15further comprising a palm at an end of the lug opposite the barrel,wherein the palm is configured to connect the lug to electricalequipment.
 18. The cable lug of claim 17 further comprising at least onebolt movably mounted in a sidewall of the barrel opposite the curvedinsert that is configured to retain the conductor in the bore betweenthe at least one bolt and the insert.
 19. The cable lug of claim 15wherein the projection and aperture are configured to limit longitudinaland rotational movement of the insert in the bore.
 20. The cable lug ofclaim 19 wherein the aperture comprises a slot in an end face of thebarrel.
 21. The cable lug of claim 20 wherein the slot comprises anL-shaped slot that provides a bayonet connection when the projection isinserted in the slot and rotated.
 22. The cable lug of claim 20 furthercomprising a palm at an end of the lug opposite the barrel, wherein thepalm is configured to connect the lug to electrical equipment.
 23. Thecable lug of claim 22 further comprising at least one bolt movablymounted in a sidewall of the barrel opposite the curved insert that isconfigured to retain the conductor in the bore between the at least onebolt and the insert.
 24. A cable lug for mounting on the end of a cablefor making electrical connection between a conductor of the cable andother electrical equipment, wherein the lug comprises a palm forconnecting the lug to the electrical equipment, a generally elongatecylindrical barrel for receiving therein one end of the cable conductor,an insert for disposal within the barrel and for extending around andalong an inner surface of the barrel, the insert being arranged to liebetween the cable conductor and the inner surface of the barrel, andmeans for retaining the insert against movement within the barrel andwherein the retaining means comprises a projection extending from theinsert at an end of the insert adjacent the opening and an aperture inan end face of the barrel at the opposite end thereof.